Research of Aerodynamic Methods of Producing Antenna Windows in a Plasma Sheath

摘要

Two aerodynamic methods of creating transmission 'windows' in typical plasma sheaths surrounding re-entry vehicles have been investigated: (1) the use of jets of coolant from flush nozzles which penetrate across the plasma slab and then mix with the ionized gases as they are carried downstream, (2) the use of a physical flow diverter to bypass some of the ionized flow laterally around the antenna. Equations are developed for the lateral jet penetration in a supersonic stream and for one-dimensional mixing for both perfect gases and real gases in thermodynamic equilibrium. The assumption of real-air equilibrium thermodynamics yields coolant requirements considerably below the perfect gas values for the jet injection method. It is concluded that the jet injection method will reduce a 200 mc. signal attenuation to 3 db. with modest jet flow rates of helium on a typical re-entry trajectory. Conversely, the use of a physical flow diverter is not an effective method of creating a transmission window where the ionization layer is not adjacent to the vehicle surface or where the attenuation needs to be reduced more than 10 db. (Author)